Using a known rat lung cDNA sequence, specific sets of primers are designed for a polymerase chain reaction (PCR) to amplify fragments of VIP receptor from a rat genomic DNA. These fragments are subcloned to make a radioactive probe to screen mRNA expression in the rat sublingual salivary gland (RSLG) and to close a complete cDNA copy from a RSLG cDNA library. After isolating a VIP receptor cDNA, the expression of cDNA and its role in signal transduction will be further investigated. This study will help to elucidate the complete pathway of salivary secretion in sublingual gland cells. KEY WORDS: cDNA, mRNA, rat sublingual gland, salivary secretion